US Patent 7116018 Electric motor

An oscillating motor has a rotor rotation of about ±15° from a rest position. The rotor has two salient poles which face a respective permanent magnet across a small air gap. The stator has a laminated stator core supporting the magnets and also two salient poles each supporting a stator coil. The stator poles confront the rotor across a small air gap between the rotor poles. When no current is flowing through the coils, the rotor rests in a rest position with the poles aligned between the north and south poles of the magnets. During operations, the stator coils induce like magnetic poles in the stator poles which in turn induce like magnetic poles in the rotor poles causing the rotor to swing towards opposite magnetic poles of the permanent magnets. When current flows in the reverse direction, the rotor swings to the opposite poles of the magnets.